Vehicle wheel alignment adjustment method

ABSTRACT

A method in which the alignment of a wheel can be easily adjusted in accordance with the characteristics of the tire, and in which a running stability appropriate for an actual road surface is obtained and a reduction in one-sided wear is achieved. A plurality of plate-like protrusions of a predetermined height are formed on the outer surface of an endless track at a predetermined distance apart in the direction of the rotation on which is rotated a wheel. When the endless track is rotated, the wheel is rotated on the tire driving surface and travels from the top surface of plate section over a step up climbing up onto the top surface of the protrusion. Next, from the top surface of the protrusion, the wheel travels over a step and descends back down onto the top surface of the plate section. This action is repeatedly executed. The longitudinal force and lateral force generated in the tire at this time are measured and a predetermined period which includes the time from when the tire is deformed as the wheel travels over the step until the tire rotates and returns substantially to its normal state is determined on the basis of the rate of change in the longitudinal force, and the wheel angle is adjusted so that the energy of the variation in the lateral force within the predetermined period is reduced.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method for adjusting the wheelalignment of a vehicle, and particularly to a method for adjusting awheel angle of a vehicle in which a wheel of a vehicle with a tirefitted thereto is rotated on a wheel rotating surface, the tire isdeformed, and the forces thereby generated are measured. The wheel angleis then adjusted on the basis of the results of the measurementproviding an improvement in the running stability of the vehicle and areduction in the wear of only one side of the tire.

2. Description of the Related Art

In general, wheels are provided with a camber angle which ensures therunning stability of the vehicle and are also provided with a toe anglefor preventing wear on only one side of the tire caused by the camberangle. In the present specification, the term “one-sided wear” is usedhereafter to describe a state where, upon observation of the state ofwear of a worn tire, it can be seen that the amount of wear extendingfrom one tread shoulder portion to the other tread shoulder portionchanges in a tapered fashion, i.e. a state where one tread shoulderportion is more worn than the central portion of the tread and the othertread shoulder portion.

Conversely, the wheel may be provided with a toe angle for balancing theforces generated at the front tires and at the rear tires therebyensuring the running stability of the vehicle and may be provided with acamber angle to prevent one-sided wear caused by the toe angle.Alternatively, the toe angle and camber angle may both be adjusted incombination to optimize the running stability of the vehicle andminimize the one-sided wear of the tire under the restraints imposed bythe vehicle such as the structural dimensions thereof and the like.

Accordingly, in order to improve the running stability of the vehicleand resistance of the tire to one-sided wear during driving, it isnecessary to adjust the toe angle and camber angle, which are the wheelangles (positional angles) provided to each wheel. In the conventionalmethod of adjusting the toe and camber angle, generally, the angle anddimensions of each wheel are measured and the measured toe and camberangles are then adjusted so as to match the target values set when thevehicle was designed.

However, while tires have various characteristics such as ply steer,which is caused by the internal construction of the tire; toe force,which is generated because the tire is at an angle to the direction inwhich the vehicle is advancing caused by the fact that the direction inwhich the wheel is rotating is different to the direction in which thevehicle is advancing; self-aligning torque, which is generated becausethe direction of advancement does not match the point on theroad-contacting surface to which the force is applied; camber thrust,which is generated when the tire deforms due to the camber angle of thewheel depending on the rigidity of the tire governed by the internalstructure of the tire; camber moment, which is generated by thedifference between the left and right sides of the road-contactingsurface; conicity, which arises from manufacturing errors inherent inindustrial products; and rolling resistance, which differs depending onthe internal structure and the material used such as the rubber, thesecharacteristics depend on and vary in accordance with the load appliedto the wheel. Further, these characteristics also depend on the type oftire.

In other words, the afore-mentioned forces are generated by thedeformation of the tire. The force generated by the tire to control itsrunning direction while causing the vehicle to advance is the sum of theafore-mentioned forces. Therefore, regardless of the type of tire, thisforce differs depending on the load distribution of the vehicle to whichthe tire is fitted and the alignment of the wheel. Accordingly, to meetthe demands for increased vehicle speed and better directionalstability, a wheel alignment adjustment method is necessary whichprovides better running stability and one-sided wear resistance.

The technology disclosed in Japanese Patent Application Publication(JP-B) No. 51-18681 is known as a conventional adjustment methodfocussing on the characteristics of the tire. The wheel is driven usinga plurality of rollers and each of the forces generated by the rollersis measured. The toe angle and camber angle are then measured on thebasis of the direction and magnitude of the measured force. However, ithas been verified that the force generated by the contact between thetire and the road differs depending on the configuration of the contactbetween the tire and the road surface. Because of this, theconfiguration of the contact between the tire and a roller are is verydifferent from the configuration of the contact between the tire and theactual road surface. Therefore, the characteristics of the forcegenerated differ greatly between the road surface and the roller.

More specifically, although the force generated using the rollerresembles the lateral force caused by the ply steer and the provision ofthe toe angle when running on an actual road surface, the alignment andthe size of the force are greatly different from those occurring whenthe wheel is run on an actual road surface. Moreover, any camber thrustis barely detectable. In addition, the forces generated in the tirearising from the deformation of the tire caused by external disturbancesfrom the numberless bumps in the road surface cannot be detected.

Accordingly, In the above-described conventional art, the measured forceexhibits values which are different from values obtained from an actualroad surface. In order to correct the measured values to the valuesobtained from an actual road surface, data expressing thecharacteristics of the respective tires on an actual road surface isneeded. Therefore the above-described conventional method lacks wideapplicability in actual practice. Further, no technical information hasbeen disclosed with regard to what angle the alignment should beadjusted to in order achieve the optimum alignment.

A technique is known in which a wheel is driven using a plurality ofrollers which aims to achieve high running stability by bringing lateralforces to substantially zero (see Japanese Patent Application Laid-Open(JP-A) No. 7-5076). In this technique, a wheel which has a camber angleis given an alignment which generates a force in the opposite directionto the direction of the camber thrust in order to bring the generatedlateral forces to zero.

However, even in this technique, in the same way as the previouslydescribed case, because the contact surface of the tire with the rollersis different from the contact surface of the tire with the actual roadsurface, any camber thrust is almost undetectable. Moreover, in order tooffset the force generated by the rotation of the wheel so as to bringthe lateral force to zero, it is necessary to apply the force from theroad surface generated by the running of the vehicle in the oppositedirection to the direction of the force generated by the vehicle. Inthis case, the deformation of the road-contacting surface of the tirebecomes even greater than when the tire is in a stationary state, andthis deformation of the road-contacting surface is a factor in thegeneration of one-sided wear of the tire.

A method has been proposed (see JP-A 8-334440) for adjusting thealignment of a wheel by rotating the wheel on a substantially planarsurface using a belt or the like, detecting the force generated by thewheel and adjusting the alignment on the basis of that force. However,an actual road surface is formed with innumerable bumps and hollows(protrusions and recesses) and a tire on a running vehicle is alwaysdeformed by these innumerable bumps and hollows. The load applied toeach wheel also varies when the vehicle is running over bumps andhollows of a comparatively long cycle also deforming each tire so thatthe tire on a running vehicle is rotating while being affected by theforce generated by the contact of the tire with the road surface and theforce from the above deformations. In contrast, the force which can bedetected by rotating the tire on a planar surface formed from a belt orthe like is only the force which is generated by the contact of the tirewith the belt surface. There is additionally none of the load variationwhich is generated by an actual road surface with the result that only aportion of the forces generated by running on an actual road surface canbe detected using the conventional method. Accordingly, even if thealignment of a wheel is adjusted on the basis of the forces detected inconditions which are unaffected by load variation such as thosegenerated by a substantially planar surface, the running stability willbe improved for a vehicle running on an extremely level surface,however, there will be no improvement in other running characteristicsand in one-sided wear.

More specifically, when a tire is running on an actual road surface,forces are generated by different generating mechanisms. In spite of thefact that these forces differ depending on the characteristics of thetire, the following conventional methods have been used: (1) a vehicleis actually run using specific tires, the angle at which one-sided wearis the least without losing running stability is found empirically, andthe wheel is adjusted to this angle; (2) the wheel is adjusted to anglewhere the force measured on a planar surface is offset to the minimumpossible (substantially zero); (3) the wheel is adjusted to an anglewhere only the specific force measured by running the wheel on a planarsurface or on rollers is the minimum possible (substantially zero); (4)the wheel is adjusted to an angle obtained through some other objectthereof is to provide a vehicle wheel alignment adjustment method whichis unaffected by the suspension geometry of the vehicle, in which anangle of a wheel can be adjusted easily to an angle of the wheel whichaccords with the characteristics of the tire and which is able to ensurerunning stability suited for an actual road surface and also reduceone-sided wear.

When a tire is rotated by contact with an uneven road surface (a roadsurface having protrusions and recesses), the tire is deformed by loadvariations generated as the tire moves vertically relative to theground-contacting surface of the tire and the lateral forces(specifically, the lateral force known as ply steer caused by thestructure of the tire, the lateral force known as conicity caused by themanufacturing process, the lateral force due to the imparting of a slipangle (toe angle) to the wheel, and the lateral force known as camberthrust due to the imparting of a camber angle to the wheel) generated onthe tire, by the deformation, all vary. In the technology disclosed inJP-A No. 10-7013, as was explained above, the angle of the wheel isadjusted on the basis of the variation in the lateral force generated inthe tire when the deformation of the tire is at maximum or substantiallymaximum as the wheel travels over a step simulating an actual roadsurface (the variation in the load is occurred at the passage of thewheel over this step).

However, because the lateral force generated in the tire varies becauseof the deformation of the tire as the load changes or as the tire passesover a step, as was explained above, then as the factors causing thesedeformations in the tire disappear, the tire, which had been in adeformed state, attempts to method. However, none of these methods canbe applied to a variety of different vehicles running on a variety ofdifferent tires.

Moreover, the present inventors measured the lateral force andlongitudinal force generated in a tire when the vehicle wheel travelsover a step and proposed a method for adjusting the wheel angle of avehicle in such a way that variation in the lateral force at the timethe longitudinal force is at a maximum or substantially maximum valuewas at a minimum (see JP-A No. 10-7013). In this method, thelongitudinal force is measured to detect the timing at which thedeformation of the tire is at maximum and the period in which thelongitudinal force is at maximum or substantially maximum is taken asthe period in which the amount of tire deformation is at maximum orsubstantially maximum.

However, the timing at which the longitudinal force changes depends onthe suspension geometry of the vehicle. The suspension geometry of thevehicle sometimes causes the timing at which the tire deformation is atmaximum or substantially maximum to fail to match up with the timing atwhich the longitudinal force of the vehicle is at maximum orsubstantially maximum. Accordingly, the accuracy of the above-describedadjustment method is affected by the suspension geometry of the vehicleand it is not always possible to adjust the alignment of the wheel tothe optimum even if the above-described method is used.

SUMMARY OF THE INVENTION

The present invention was achieved in consideration of the above and andeform back to its normal shape and this deformation also causes thelateral force to vary. The present inventors, realized from the abovefacts, come to the conclusion that by observing the variation in thelateral force during a period including not only the time during whichthe deformation of the tire is at maximum or substantially maximum, butalso the time during which the tire attempts to deform back to itsnormal state, and by adjusting the wheel alignment (adjusting the angleof the wheel) so that the energy of the variation in the lateral forceover the above-described period is at a minimum, a higher degree ofrunning stability suitable for an actual road surface and a furtherreduction in one-sided wear could be achieved.

In order to veri the above discovery, the present inventors performedthe experiment described below. Specifically, a tire was rotated using atire driving apparatus having, in at least one position on thetire-driving surface thereof in the direction in which the tire drivingapparatus is driven to rotate, a planar protrusion whose length in thedirection of rotation is long enough for the tire to sit completelythereon and whose length in the axial direction of the rotation which isorthogonal to the direction of rotation is larger than the width of thetire. (By this structure, a step is formed at the front and the rear ofthe planar protrusion along the direction of the rotation on the tire-driving surface.) The lateral force generated in the tire is measuredrepeatedly in short cycles. Then from the results of the measurement ofthe lateral force during each cycle (each measurement time) which iswithin a predetermined period which includes the time from the momentthe tire is deformed as the wheel passes over the step until the tirerotates and substantially returns to its normal state, the sum of thesquare root of the rate of change (the value of the primary differentialfor the time of the lateral force) in the lateral force , as the energyof the variation in the lateral force within the above predeterminedperiod, in each measurement time is repeatedly obtained while thealignment (in this experiment, the toe angle) of the wheel is alteredeach time by a predetermined amount.

FIG. 1 shows the relationship obtained by the above experiment betweenthe toe angle and the energy of the variation in the lateral forcegenerated in the tire within the predetermined period. As is clear fromFIG. 1, the above experiment confirmed that a definite correlationexists between the toe angle and the energy of the variation in thelateral force. Confirmation was also made that when the toe angle of thevehicle was adjusted so that the energy of the variation in the lateralforce was at the minimum, the running stability of the vehicle wasimproved greatly and one-sided wear was greatly reduced.

The present inventors also compared and evaluated the running stabilityof several different models of vehicle (vehicles 1 to 4) under two typesof adjustment mode. One mode was with the wheel angle adjusted to theangle determined when the vehicle was designed (standard mode); thesecond mode, as in the experiment described above, was with the wheelangle adjusted so that the energy of the variation in the lateral forcegenerated in the tire during a predetermined period including the timefrom when the tire is deformed by the wheel travelling over a step untilthe tire rotates and returns substantially

TABLE 1 Straight Line Riding Straight Line Progression Comfort onProgression (Undulating Cornering Rough One-sided Evaluated Vehicle(Flat Road) Road) Wandering Stability Surfaces Wear Vehicle 1 PresentMode 9.0 8.5 8.0 8.0 7.0 98 Standard Mode 8.5 7.0 6.5 6.5 6.5 80 Vehicle2 Present Mode 8.5 8.5 8.0 7.5 8.0 98 Standard Mode 6.0 6.5 6.5 6.5 6.560 Vehicle 3 Present Mode 8.0 8.0 8.0 8.5 6.5 97 Standard Mode 6.5 7.06.5 6.5 5.5 79 Vehicle 4 Present Mode 9.0 8.5 8.5 7.5 7.5 99 StandardMode 8.0 7.5 8.0 7.5 6.5 85

to its normal state was at a minimum (the present mode). The vehiclesused as vehicles 1 to 4 all had a displacement of between 1600cc and3000cc and had either an FF or FR drive system (i.e. passengervehicles). The tires used were all models sold on the general market ofa size appropriate to the vehicle to which they were fitted. The resultsof the experiment are shown in Table 1. The standards by which theresults were evaluated are shown in Table 2.

TABLE 2 Evaluation Level 6 Barely Acceptable 7 Somewhat Acceptable 8Acceptable 9 Very Acceptable Level of Difference in Evaluated ±0.5Slight Difference Point ±1.0 Difference 2 Substantial DifferenceEvaluation of One-sided Wear One-sided Wear Ratio = Shoulder Wear/CenterWear × 100 (The larger of the one-sided wear ratios of each wheel istaken and the average value of all four wheels of each vehicle is shownin the evaluation table)

Amount of abrasion compared at point A and point B 45% ofroad-contacting area

As is clear from Table 1, the above experiment verified that, byadjusting the wheel angle so that the energy of the variation in thelateral force generated in the tire during a predetermined periodincluding the time from when the tire is deformed by the wheeltravelling over a protrusion (a raised step) until the tire rotates andreturns substantially to its normal state is at a minimum, thenregardless of the type of tire, the running stability of the vehicle canbe greatly improved, and one-sided wear can also be greatly reduced.

Accordingly, the present inventors discovered from the above experimentthat, by measuring at least the lateral force generated in a tire whenthe tire is rotated by being in contact with a wheel rotating surface onwhich is formed a step and obtaining the energy of the variation in thelateral force generated in the tire in the above-described predeterminedtime, it was possible to obtain the optimum wheel angle in accordancewith the characteristics of the tire on the basis of the above obtainedenergy of the variation in the lateral force. Further, the presentinventors also discovered that if the wheel angle of a vehicle wasadjusted to the optimum wheel angle obtained in this manner, then arunning stability suitable for an actual road surface and a reduction inone-sided wear could be achieved.

On the basis of the above, in the wheel alignment adjustment methodaccording to the first aspect of the present invention, a vehicle and awheel rotating surface are moved relative to each other in such a mannerthat a wheel of a vehicle to be adjusted with a tire fitted thereto isrotated in a proceeding direction of the vehicle over the wheel rotatingsurface which has a step of a predetermined height formed thereon sothat the wheel passes over the step, and a lateral force generated inthe tire of the wheel is measured, and

a wheel angle is adjusted so that an energy of a variation in thelateral force generated in the tire during a predetermined periodincluding a time from when the tire is deformed at the wheel passingover the step until the tire rotates and returns substantially to itsnormal state is within a predetermined range which includes the minimumvalue of the energy of the variation.

In the first aspect of the present invention, a vehicle and a wheelrotating surface are moved relatively in such a manner that a wheel of avehicle to be adjusted with a tire fitted thereto is rotated in aproceeding direction of the vehicle over the wheel rotating surfacewhich has a step of a predetermined height formed thereon so that thewheel passes over the step, and a lateral force generated in the tire ofthe wheel is measured. Note that, in the present invention, lateralforce means the force running in the direction of a line intersecting aplane which includes the axis orthogonal to the forward direction (thedirection of the relative movement between the vehicle and the wheelrotating surface) of the vehicle and the wheel rotating surface (theroad surface). Next, in the first aspect of the present invention, awheel angle is adjusted so that an energy of a variation in the lateralforce generated in the tire during a predetermined period including atime from when the tire is deformed at the wheel passing over the stepuntil the tire rotates and returns substantially to normal state iswithin a predetermined range (for example a range from the minimum valueto a predetermined value) which includes the minimum value of the energyof the variation. (preferably, the wheel angle is adjusted so that theenergy of the variation in the lateral force is the minimum in theadjustable range of the vehicle to be adjusted. However, there are alsovehicles whose energy of the variation in the lateral force cannot beadjusted to the minimum because the wheel angle adjustment pitch (thevalue of the smallest changeable angle) is at variance due to the typeof model (structure) and the like of the vehicle to be adjusted.)

Accordingly, as was clear from the results of the experiment describedabove, the wheel angle (positional angle) can easily be adjusted to analignment which accords with the characteristics of the tire. Moreover,a running stability suitable for an actual road surface and reducedone-sided wear can also be obtained. Further, in the first aspect of thepresent invention, because the wheel angle is adjusted on the basis ofthe energy of the variation in the lateral force generated in the tirewithin a predetermined period which includes the time from when the tireis deformed due to the wheel travelling over a step until the time thetire rotates and substantially returns to its normal state, there is noreduction in the accuracy of the wheel alignment adjustment due to thesuspension geometry of the vehicle in comparison with when the wheelangle is adjusted on the basis of the lateral force during the periodwhen the longitudinal force generated in the tire is at maximum orsubstantially maximum, as was disclosed in JP-A 10-7013.

The predetermined period which includes the time starting from when thetire is deformed at the wheel travelling over a step until the tirerotates and substantially returns to its normal state may be determinedby, for example, detecting the start of a predetermined period bydetecting the displacement of the wheel and then detecting the finish ofthe predetermined period by measuring the elapsed time from thepredetermined start, however, this method may require a complicatedmechanism to determine the predetermined period and the errors may occurin the determination of the predetermined period in some cases.

Because of this, in the vehicle wheel alignment method according to thesecond aspect of the present invention, a vehicle and a wheel rotatingsurface are moved relative to each other in such a manner that a wheelof a vehicle to be adjusted with a tire fitted thereto is rotated in aproceeding direction of the vehicle over the wheel rotating surfacewhich has a step of a predetermined height formed thereon so that thewheel passes over the step, and at least one of a longitudinal force ora load generated in the tire and a lateral force generated in the tireof the wheel are each measured,

a predetermined period including a time from when the tire is deformed,at the wheel passing over the step, until the tire rotates and returnssubstantially to its normal state is determined on the basis of theresults of the measurement of at least one of the longitudinal force orthe load, and

a wheel angle is adjusted so that an energy of a variation in thelateral force generated in the tire during the predetermined period iswithin a predetermined range which includes the minimum value of theenergy of the variation.

In the second aspect of the present invention, a vehicle and a wheelrotating surface are moved relative to each other in such a manner thata wheel of a vehicle to be adjusted with a tire fitted thereto isrotated in a proceeding direction of the vehicle over the wheel rotatingsurface which has a step of a predetermined height formed thereon sothat the wheel passes over the step, and a lateral force generated inthe tire of the wheel is measured, at least one of a longitudinal forceor a load generated in the tire , and the lateral force generated in thetire of the wheel are each measured, a predetermined period isdetermined on the basis of the results of the measurement of at leastone of the longitudinal force or the load. Note that the longitudinalforce according to the present invention is the force in a directionrunning along a line intersecting a plane which includes the axisrunning in the direction in which the vehicle travels forward (thedirection in which the vehicle moves relative to the wheel rotatingsurface) and the wheel rotating surface (the road surface), while theload according to the present invention is the force in a verticaldirection applied to the wheel rotating surface (the road surface).

The longitudinal force and the load can both be easily measured byproviding a sensor on the wheel rotating surface, a member connected tothe wheel rotating surface, or on the wheel which is to be adjusted (inthe same way as the lateral force). Moreover, provided that the vehicleis the same, the transition of the longitudinal force and the loadgenerated in the tire (i.e. the waveform) as the wheel rotates andtravels over the step undergo almost no change even if the alignment ofthe wheel is altered. Accordingly, a predetermined period can beaccurately determined by basing the determination on the results of themeasurement of the longitudinal force or the load, even when the lateralforce and the longitudinal force or the load is measured and the wheelangle is adjusted repeatedly.

In the second aspect of the present invention, because the wheel angleis adjusted so that the energy of the variation in the lateral forcegenerated in the tire inside the predetermined period is within apredetermined range which includes the minimum value of the energy (forexample, a range between the minimum value and a predetermined value),the wheel angle can be easily adjusted to an alignment which accordswith the characteristics of the tire without being affected by thesuspension geometry of the vehicle in the same way as in the firstaspect of the present invention, and both running stability suitable foran actual road surface and a reduction in the one-sided wear of a tirecan be obtained.

Note that the present inventors obtained the energy of the variation inthe lateral force by repeating the measurement of the lateral force whenthe vehicle traveled over the step as it rotated. They altered thealignment of the wheel, for both the portion of the step where theheight of the step decreases at the edge of the step when looking alongthe direction in which the wheel rotates (here called “the downwardstep” for convenience), and where the height of the step increases atthe edge of the step when looking along the direction in which the wheelrotates (here called “the upward step” for convenience). As a result, itwas confirmed that the energy of the variation in the lateral forcegenerated in the tire inside the predetermined period is changed muchmore by changing the alignment of the wheel when the wheel travels overthe upward step than when the wheel travels over the downward step.

Therefore, in the third aspect of the present invention in the first orsecond aspects of the present invention, the wheel rotating surfacecomprises:

a base surface; and

a protruding surface which is positioned on the downstream side of thebase surface in a direction in which the wheel rotates, and whose heightat least at a position where the step is formed by the base surface andthe protruding surface is greater than the base surface by apredetermined amount.

According to the third aspect of the present invention, because theupward step is formed in the wheel rotating surface, by adjusting thewheel angle on the basis of the energy of the variation in the lateralforce inside the predetermined period which includes the time from whenthe tire is deformed by the wheel traveling over the upward step untilthe tire rotates and substantially returns to its normal state, thewheel angle (the alignment of the wheel) can be adjusted with a highamount of accuracy.

In the fourth aspect of the present invention in the third aspect of thepresent invention, the protruding surface is a top surface of asubstantially plate protrusion whose height is a predetermined heightabove the base surface, and the protrusion is formed so that theprotruding surface extends long enough in a direction of a relativemovement of the vehicle and the wheel rotating surface for both ends ofa ground-contacting portion of the tire in the direction of the relativemovement to be in contact with the protruding surface when the wheelpasses over the protrusion.

Note that, in the third aspect of the present invention, it is possibleto form only the upward step in the wheel rotating surface, however, asis described in the fourth aspect, it is also possible to form an upwardstep at one end of the protrusion and a downward step at the other endof the protrusion in the direction in which the wheel rotates byproviding a plate-like protrusion whose height is greater than the basesurface by a predetermined amount. Note also that the upper surface ofthe protrusion in the fourth aspect of the present invention correspondsto the protruding surface described in the third aspect.

In the fourth aspect of the present invention, the protrusion is formedso that the protrusion is formed so that the protruding surface extendslong enough (preferably, the top surface of the protrusion extends fortwice the above length in the direction of relative movement of thevehicle and the wheel rotating surface. More preferably, the top surfaceof the protrusion extends for three times the above length in thedirection of relative movement of the vehicle and the wheel rotatingsurface) in a direction of a relative movement of the vehicle and thewheel rotating surface for both ends of a ground-contacting portion ofthe tire in the direction of the relative movement to be in contact withthe protruding surface when the wheel passes over the protrusion.Because of this, a tire which is deformed by the wheel travelling overan upward step onto the top of the surface of the protrusion is able tomomentarily return to substantially its normal state on the top of thesurface of the protrusion before the wheel drops down from the topsurface of the protrusion.

It should be noted here that it is sufficient if the wheel rotatingsurface according to the present invention has a step formed thereon andthe wheel is able to be rotated thereon. Namely it may be also possiblefor a member to be placed on the flat surface of a road or the like inorder to form the step, however, a wide area is needed for the car torun in during the measurement, and the speed of the rotation of thewheel is needed to keep constant during the measurement. Therefore, inthe fifth aspect of the present invention in the first or second aspectsof the present invention, the wheel rotating surface is an outerperipheral surface of an endless track which is driven to rotate, andthe step is provided at least at one location on the wheel rotatingsurface along a direction in which the endless track rotates, and

the wheel of the vehicle to be adjusted is placed on the wheel rotatingsurface and the endless track is driven to rotate so that the wheel ofthe vehicle to be adjusted is rotated, thereby moving the vehicle andthe wheel rotating surface relative to each other.

In the fifth aspect of the present invention, because the outerperipheral surface of the endless truck (belt) which is driven to rotateis used for the wheel rotating surface and a step is provided at leastat one location on the wheel rotating surface along the direction inwhich the endless track rotates, and because a wheel of the vehicle tobe adjusted is placed on the wheel rotating surface and the endlesstruck is driven to rotate so that the wheel of the vehicle to beadjusted is rotated, thereby moving the vehicle and the wheel rotatingsurface relative to each other, the vehicle is stationary when thevehicle and the wheel rotating surface are moved relative to each othernegating the requirement for a large area for the vehicle to travel induring the measurement. Accordingly, the wheel alignment adjustment ofthe present invention is able to be performed in a small area. Moreover,by controlling the speed of the rotation of the endless track, themaintaining of a constant speed of the rotation of the wheel during themeasurement is easily achieved.

FIG. 2 shows the transition of the primary differential value (dFx/dt)in relation to the time t of the longitudinal force Fx and the primarydifferential value (dFy/dt) in relation to the time t of the lateralforce Fy when the longitudinal force Fx and the lateral force Fy aremeasured by a method in which a step (an upward step and downward step)is formed in a wheel rotating surface by providing a planar-likeprotrusion, such as that described in the fourth aspect, and the vehicleand wheel rotating surface are moved relative to each other in such away that the wheel rotates on the wheel rotating surface in thedirection in which the vehicle moves forward and travels over theprotrusion (travels over the upward step, rotates over the top surfaceof the protrusion (the protruding surface), and then travels down thedownward step). FIG. 3 shows the transition of the primary differentialvalue (dFz/dt) in relation to the time t of the load Fz and the primarydifferential value (dFy/dt) of the lateral force Fy when the load Fz andthe lateral force Fy are measured under the same conditions as for FIG.2.

Note that the (two) locations in FIG. 2 where the primary differentialvalue of the longitudinal force suddenly undergoes a huge change in thepositive or negative direction and the (two) locations in FIG. 3 wherethe primary differential value of the load suddenly undergoes a hugechange in the positive or negative direction indicate the variation inthe longitudinal force and the load caused by the deformation of thetire which occurs when the wheel travels over the upward step or thedownward step. The area between the locations in FIGS. 2 and 3 where theprimary differential value of the longitudinal force and the primarydifferential value of the load undergo a huge change corresponds to whenthe wheel is rotating on the top surface of the protrusion (theprotruding surface) and the tire is in the process of returning tosubstantially its normal state, and, as is clear from FIGS. 2 and 3, theprimary differential value of the longitudinal force and the primarydifferential value of the load are still changing during this time, evenif only slightly. Consequently, it order to determine from thelongitudinal force or the load (or from the primary differential valueof the longitudinal force or load) whether the tire has returned tosubstantially its normal state, easier, the sixth aspect of the presentinvention is provided.

In the sixth aspect of the present invention in the second aspect of theinvention, the protruding surface is a top surface of a substantiallyplate shaped protrusion whose height is a predetermined height above thebase surface, and the protrusion is formed so that the protrudingsurface extends long enough in a direction of a relative movement of thevehicle and the wheel rotating surface for both ends of aground-contacting portion of the tire in the direction of the relativemovement to be in contact with the protruding surface when the wheelpasses over the protrusion, and

the predetermined period is determined to be a period from a firsttiming until a second timing, the first timing is when a rate of achange at least one of in the longitudinal force or the load as thewheel climbs up onto the protrusion with the tire of the wheel deformingbecomes the minimum after changing to a predetermined value or more, thesecond timing is one of when the rate of the change at least one of inthe longitudinal force or the load becomes to the minimum after changingto a predetermined value or more, or when a front end of theground-contacting portion of the tire in the direction of the relativemovement is without contacting with the protruding surface as the tirerotates on the protruding surface and the wheel descends from theprotrusion with the tire of the wheel deforming.

In the sixth aspect of the present invention, the time when the rate ofthe change (the primary differential value) of the longitudinal force orload caused by the tire on a wheel deforming as the wheel climbs up ontothe protrusion becomes the minimum (for example, substantially “0”)after changing to a predetermined value or more is taken as the firsttiming (the timing indicated by P₁ in FIGS. 2 and 3), and the time whenthe rate of the change in the longitudinal force or the load caused bythe tire on a wheel deforming as the wheel descends from the protrusionafter the tire has rotated on the protruding surface becomes the minimum(namely, substantially “0”) after changing to a predetermined value ormore (the timing indicated by P₂ in FIGS. 2 and 3), or the time when thefront end of the ground-contacting portion of the tire in the directionof the relative movement is not in contact with the protruding surface(for example, the timing which corresponds to the peak of the portion ofthe primary differential value of the longitudinal force or loadchanging to a predetermined value or more immediately before P₂) istaken as the second timing. Because the period from the first timinguntil the second timing is determined to be the predetermined period,the first timing and second timing can be determined easily and with ahigh degree of accuracy from the results of the measurement of thelongitudinal force or load, thus enabling the predetermined period to bedetermined with a high degree of accuracy.

Note that in the first and second aspects of the present inventiondescribed above, the tire is deformed by causing the tire to travel overa step formed in a wheel rotating surface. However, it is possible toinstead deform the tire by changing the load acting on the tire. Namely,in the vehicle wheel alignment adjustment method according to theseventh aspect of the present invention, the wheel having the tirefitted thereto of the vehicle to be adjusted is rotated on the wheelrotating surface in the direction in which the vehicle moves forward, awheel of a vehicle to be adjusted with a tire fitted thereto is rotatedon a wheel rotating surface in a proceeding direction of the vehicle,

a load acting on the vehicle is changed by a predetermined amount ormore within a predetermined period, and a lateral force generated in thetire on the wheel is measured, and

a wheel angle is adjusted in such a way that an energy of a variation inthe lateral force generated in the tire during a predetermined periodwhich includes a time from when the tire of the wheel is deformed with achange in the load until the tire rotates and returns substantially tonormal state is within a predetermined range which includes the minimumvalue of the energy of the variation.

In the vehicle wheel alignment adjustment method according to the eighthaspect of the present invention in the seventh aspect of the presentinvention, the wheel rotating surface is a substantially planar surface,and

the vehicle and the wheel rotating surface are rotated relative to eachother in such a way that the wheel rotates on the wheel rotatingsurface, the load acting on the wheel is changed by displacing the wheelin substantially a vertical direction via the wheel rotating surface,and the load and lateral force generated in the tire of the wheel areeach measured, and

the predetermined period is determined by comparing the result of themeasurement of the load with a load generated in the tire when the tireof the wheel is substantially normal state.

In the seventh aspect of the present invention, the wheel is rotated andthe tire is deformed by changing the load acting on the tire by apredetermined amount or more within a predetermined time. Changing theload acting on the wheel in this way is achieved by rotating the wheelon the substantially planar wheel rotating surface, as, for example,described as the eighth aspect, and displacing the tire in substantiallya vertical direction via the wheel rotating surface.

In the seventh aspect of the present invention, because the wheel angleis adjusted in such a way that the energy of the variation in thelateral force generated in the tire inside a predetermined period whichincludes the time from when the tire is deformed with the change in theload until the tire rotates and returns substantially to its normalstate is within a predetermined range which includes the minimum valueof the energy of the variation, in the same way as in the first andsecond aspects of the present invention, the adjustment is not affectedby the suspension geometry of the vehicle, the wheel angle is easilyadjusted to an alignment which accords with the characteristics of thetire, and both a running stability suitable for an actual road surfaceand a reduction in one-sided wear are achieved.

Note that when the tire of a wheel rotating on the wheel rotatingsurface is deformed by displacing the wheel in substantially a verticaldirection via the wheel rotating surface as described above, thelongitudinal force of the tire may not exhibit the same clear change inthe deformation of the tire as that shown in FIG. 2. For this reason,when the tire is deformed by displacing the wheel via the wheel rotatingsurface, it is preferable if the predetermined period (the period fordetermining the energy of the variation of the change in the lateralforce generated in the tire) is determined by measuring both the loadand the lateral force generated in the tire on the wheel, as in theeighth aspect of the present invention and, from the results of themeasurement, comparing this load to the load generated in the tire whenthe tire on the wheel is substantially in a normal state.

In the vehicle wheel alignment adjustment method according to ninthaspect of the present invention in any one of the first, second, orseventh aspects of the present invention, a plurality of measurementsare made of the lateral force in a period for measuring the lateralforce, and

the energy of the variation in the lateral force generated in the tireof the wheel within the predetermined period is determined bycalculating and adding of, on the basis of the lateral force measured ateach measurement within the predetermined period, at least one of thesquare root of the primary differential value of the lateral force ateach measurement, or the absolute value of the primary differentialvalue of the lateral force at each measurement, or the secondarydifferential value of the lateral force, or the square root of thesecondary differential value of the lateral force, or the absolute valueof the secondary differential value of the lateral force, or thetertiary differential value of the lateral force, or the square root ofthe tertiary differential value of the lateral force.

Moreover, in any one of the first, second, or seventh aspects of thepresent invention, the computation of the energy of the variation in thelateral force generated in the tire on a wheel within a predeterminedperiod, as described in the ninth aspect of the present invention, hasspecifically, for example, making a plurality of measurements of thelateral force in the period for measuring the lateral force anddetermining the energy of the variation by computing and adding, on thebasis of the lateral force measured at each measurement within thepredetermined period, either the square root of the primary differentialvalue of the lateral force at each measurement, or the absolute value ofthe primary differential value of the lateral force at each measurement,or the secondary differential value of the lateral force, or the squareroot of the secondary differential value of the lateral force, or theabsolute value of the secondary differential value of the lateral force,or the tertiary differential value of the lateral force, or the squareroot of the tertiary differential value of the lateral force.

In the vehicle wheel alignment adjustment method according to the tenthaspect of the present invention, a vehicle and a wheel rotating surfaceare moved relatively in such a manner that a wheel of a vehicle to beadjusted with a tire fitted thereto is rotated in a proceeding directionof the vehicle over the wheel rotating surface with a tire of a wheeldeforming, and a lateral force generated in the tire of the wheel ismeasured, and a wheel angle is adjusted so that an energy of a variationin the lateral force generated in the tire during a predetermined periodincluding a time from when the tire is deformed until the tire rotatesand returns substantially to normal state is within a predeterminedrange which includes the minimum value of the energy of the variation.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a line graph showing an example of the relationship betweenthe alignment of the wheel (the toe angle) and the energy of thevariation in the lateral force generated in the tire within apredetermined period which includes the time from when the tire isdeformed as the wheel travels over the step until the tire rotates andreturns substantially to its normal state.

FIG. 2 is a line graph showing examples of the transition of the primarydifferential value of the longitudinal force generated in the tire whenthe wheel travels over the upward step and then the downward step andthe transition of the primary differential value of the lateral forcegenerated in the tire when the wheel travels over the upward step andthen the downward step.

FIG. 3 is a line graph showing examples of the transition of the primarydifferential value of the load generated in the tire when the wheeltravels over the upward step and then the downward step and thetransition of the primary differential value of the lateral forcegenerated in the tire when the wheel travels over the upward step andthen the downward step.

FIG. 4 is a side view of the wheel alignment measuring apparatusaccording to the present embodiment.

FIG. 5 is a schematic plan view of the wheel alignment measuringapparatus.

FIG. 6 is a plan view of the tire driving apparatus.

FIG. 7A is a cross-sectional view taken along the line 7A in FIG. 6.

FIG. 7B is a cross-sectional view taken along the line 7B in FIG. 6.

FIG. 8A is a front view of a force sensor.

FIG. 8B is a side view of a force sensor.

FIG. 9 is a schematic structural view of the drive mechanism of a wheellocking plate.

FIG. 10 is a schematic diagram showing the position adjusting mechanismof a distance sensor and tire driving apparatus.

FIG. 11 is a flow chart showing the wheel alignment measurement process.

FIG. 12 is a flow chart showing the vehicle orientation adjustmentprocess.

FIG. 13 is an explanatory diagram showing how the vehicle orientation isadjusted.

FIG. 14 is a schematic cross-sectional diagram showing another exampleof a tire driving apparatus.

FIGS. 15A through 15C are schematic diagrams of further examples of tiredriving appartuses.

FIG. 16 is a perspective view showing an example of a mechanism formoving a tire driving apparatus in a vertical direction.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

An example of the present embodiment will now be explained in detailwith reference to the drawings. A vehicle wheel alignment measuringapparatus capable of being used in the present invention is shown inFIGS. 4 and 5.

This wheel alignment measuring apparatus is provided with a mountingtray 12 which is raised and lowered by a main lifting apparatus 10, anda vehicle supporting tray 16 which is raised and lowered by asub-lifting apparatus 14 in comparison with the reference height of themounting tray 12. Four tire driving apparatuses 18 are attached to themounting tray 12 to drive and rotate each wheel of a vehicle 20. Thefour tire driving apparatuses 18 each have the same structure, so onlyone tire driving apparatus 18 will be explained below.

As is shown in FIG. 6, the tire driving apparatus 18 is provided with aframe 22 comprising a pair of main frames 22A disposed in parallel witheach other at a predetermined distance apart, and side plates 22Bextending between the pair of main frames 22A at both ends thereof. Theframe 22 is positioned so that the longitudinal direction of the mainframes 22A extends in the longitudinal direction of the vehicle 20. Apair of driving shafts 24 are entrained between the pair of main frames22A at positions in the vicinity of each side plate 22B. The pair ofdriving shafts 24 are rotatably supported by the main frames 22A.

Gears 26 are attached to one end of each of the driving shafts 24. Thegears 26 are connected via an unillustrated driving force transmittingmechanism to a rotating shaft of an unillustrated motor whose drivingaction is controlled by a control device 80 (see FIG. 5). Accordingly,when the motor is driven, the driving force generated by the motor istransmitted to the driving shafts 24 via the driving force transmittingmechanism and the gears 26, thus causing each of the driving shafts 24to rotate.

Two sprockets 28 are attached opposite each other at each end of both ofthe pair of driving shafts 24. Two endless chains 30 are entrainedbetween the pair of driving shafts 24 and are also entrained aroundopposing pairs of the sprockets 28 (see FIG. 7B). Thus, when the drivingshaft 24 rotates, the two chains 30 are also rotated via the sprocket28.

The tire driving apparatus 18 is provided with a plurality of elongatedsections of aluminum plate 32 whose width is sufficient that they do notget pushed into the grooves in the tread pattern of the tire, and whoselength is sufficiently longer than the width of the tire. The pluralityof plate sections 32 are each disposed one next to the other in parallelwith the side plates 22B along the longitudinal direction of the chains30, and have one end thereof attached to one of the chains 30 and theother end thereof attached to the other chain 30 via an unillustratedconnecting member.

Accordingly, as is shown in FIGS. 6 and 7, an endless track 34 is formedby connecting together a plurality of plate sections 32 in the widthwisedirection of the plate sections 32 using the chain 30 and the connectingmembers. The endless track 34 is entrained between the pair of drivingshafts 24 in such a way that the longitudinal direction of the platesections 34 is the transverse direction of the vehicle 20. The pair ofdriving shafts 24 is supported by the frame 22, the endless track 34 issupported in a rotatable manner by the frame 22. Note that the surfaceformed by the upper surface of the plurality of plate sections 32 whenlooking at the tire driving apparatus 18 from above is hereafter calledthe tire driving surface 36 (this corresponds to the wheel rotatingsurface of the present invention).

As is shown in FIGS. 7A and 7B, a plurality of planar protrusions havinga predetermined height are formed at a predetermined distance from eachother in the direction in which the endless track 34 rotates on theouter surface of the endless track 34. Each protrusion 38 is formed onthe top surface of two plate sections 32, i.e. on the outer surface ofthe endless track 34, in such a way that the protrusion 38 extendsacross the two adjacent plate sections 32 in the direction in which theendless track 34 rotates. The length of each protrusion 38 in thewidthwise direction of the endless track 34 (the direction of rotation)is longer than the width of the tire.

When the endless track 34 is rotated, each plate section 32 moves in thedirection of rotation. However, when each of the two adjacent platesections 32 having the protrusions 38 formed thereon is moved to theposition which corresponds to the tire driving surface 36 of the endlesstrack, the top surfaces of the two plate sections 32 become flush witheach other. Therefore, the top surfaces of the two protrusions 38 formedon the top surfaces of the two plate sections 32 also become flush witheach other and also become contiguous with each other. Accordingly, asingle protruding portion is formed extending across a predeterminedlength (the length is two or three times the length in the direction ofrotation of the road-contacting portion of the tire on the wheel mountedon the tire driving surface 36) in the direction in which the endlesstrack 34 rotates.

This protruding portion (the protruding portion comprised of the twoprotrusions 38) corresponds to the protrusion described in the fourthaspect of the present invention, while both edges of the protrudingportion in the direction in which the endless track 34 rotatescorrespond to the step of the present invention. Note that, below, ofthe two edges, the edge which is positioned upstream from the protrusion38 in the direction in which the wheel rotates on the tire drivingsurface 36 (the opposite direction to the direction in which the endlesstrack 34 rotates) is called the upwards step (the step described in thethird aspect of the present invention), while the edge on the other sideof the protrusion 38 is called the downwards step.

Due to the above structure, when the endless track 34 is rotated while awheel of the vehicle 20 is mounted on the tire driving surface 36thereof, the tire rotates on the tire driving surface 36 and travelsfrom the top surface of the plate sections 32 over the step and climbsup onto the top surface (the protruding surface) of the protrudingportion. Next, the tire travels over the step from the top surface ofthe protruding portion and descends onto the top surface of the platesections 32 (the base surface). This process is repeated.

As is shown in FIG. 7A, a planar guide 40 is attached to each endportion of the surface of each plate section 32 on the inner side of theendless track 34. A V-shaped engaging groove 40A is carved in eachplanar guide 40 running in the direction in which the endless track 34rotates. Further, the end portions of a load bearing plate member 42disposed so as to extend across the pair of main frames 22A are fixed tothe internal surface of the pair of main frames 22A. On the top surfaceof this load bearing plate member 42 is fixed a guide member 44 at aposition facing the planar guide 40.

V-shaped receiving grooves 44A are carved in the top surface of theguide member 44 at positions opposite the engaging grooves 40A runningin the direction in which the endless track rotates. A plurality ofsteel balls 46 of identical size are provided between the engaginggrooves 40A and the receiving grooves 44A.

Accordingly, even if the wheel of a vehicle 20 is mounted on the tiredriving surface 36 thus applying a load to the plate sections 32 formingthe endless track 34, the plurality of plate sections 32 forming thetire driving surface 36 are supported by the load bearing plate member42 and the guide member 44 via the balls 46 in such a way that the uppersurface of the plurality of plate sections 32 is an unchanging flatsurface. Moreover, by driving the endless track 34 and rotating thewheel, as is described below, the force in the direction in which theendless track rotates acts on the tire driving surface 36 and istransmitted to the frame 22 via the planar guides 40, the balls 46, theguide plates 44, and the load bearing plate member 42.

Rectangular-shaped rectangular grooves 42A are formed in the portion ofthe top surface of the load bearing plate member 42 covered by the guidemember 44. The size of the rectangular grooves 42A is such as to allowthe balls 46 to pass along the rectangular grooves 42A in the directionin which the endless track 34 rotates. A U-shaped groove (notillustrated) is formed in both end portions of the load bearing platemember 42 running in the direction in which the endless track circulatesextending in a U shape between the path between the engaging groove 40Aand the receiving groove 44A and the path formed by the rectangulargroove 42A. The balls 46 rotate via the U-shaped groove along the pathbetween the engaging groove 40A and the receiving groove 44A and thepath formed by the rectangular groove 42A.

A supporting frame 48 is provided at the external side of the frame 22.The supporting frame 48 is formed in a substantially U shape comprisinga bottom portion 48A positioned beneath the frame 22 and extending inthe direction in which the endless track 34 is rotated, and a pair ofsupporting portions 48B extending upright from both end portions of thebottom portion 48A so that the sides thereof face the side plates 22B ofthe frame 22 at a predetermined distance therefrom. Left and rightsliding guide rails 50 are attached to each side surface of the pair ofsupporting members 48B extending in the direction in which the endlesstrack 34 rotates (the transverse direction of the vehicle).

Moving blocks 54 are attached to the side plates 22B of the frame 22 viaforce sensors 52, which are explained in detail below. Grooves, whichfit together with the left and right sliding guide rails 50 are carvedin the side surfaces of the moving block 54 and the moving block isfitted together with the left and right sliding guide rails 50 via thesegrooves. Accordingly, the frame 22 (and also the endless track 34) isable to move in the transverse direction of the vehicle along the leftand right sliding guide rails 50.

A bracket 56 is attached to one of the pair of side plates 22Bprotruding towards the supporting portion 48B of the supporting frame48. A threaded hole penetrates the distal end portion of the bracket 56in the transverse direction of the vehicle. A threaded rotating shaft 58is screwed into the threaded hole creating a ball-screw mechanism. Oneend of the rotating shaft 58 is coaxially connected to the rotatingshaft of a motor 60 mounted on the supporting plate 48B of thesupporting frame 48. The motor 60 is connected to the control device 80(see FIG. 5) and the driving of the motor is controlled by the controldevice 80.

Because of this, when the rotating shaft is rotated by the driving ofthe motor 60, the bracket 56, the frame 22, and the endless track aremoved as a single unit closer to or further from the supporting frame 48in the transverse direction of the vehicle. Moreover, when the drivingof the motor has been halted, movement of the frame 22 and the othermembers closer to or further from the supporting frame 48 in thetransverse direction of the vehicle is prevented by the action of theball-screw mechanism.

As is shown in FIGS. 8A and 8B, the force sensor 52 is provided with apair of force measuring beams 52A which are equipped with forcedetecting elements such as distortion gauges and load cells. Both endsof each force measuring beam 52A are fixed to the inner portion of arectangular frame 52C. The middle portions of each force measuring beam52A are mutually connected by a connecting plate 52B. The force sensor52 detects the force in two directions orthogonal to the longitudinaldirection of the force measuring beam 52A (the direction orthogonal tothe surface of the sheet of paper in FIG. 8A and the directionorthogonal to the surface of the sheet of paper in FIG. 8B).

Four screw holes are provided in the side plates 22B for mounting to therectangular frame 52C, and four holes are provided in the connectingplate 52B for mounting to the moving block 54. The force sensor 52 isbolted to the side plates 22B and the moving block 54 in such a way thatthe longitudinal direction of the force measuring beam 52A faces in thevertical direction of the vehicle.

Accordingly, when the endless track 34 is rotated and a force is appliedin the direction in which the endless track 34 rotates due to thevehicle wheel rotating on the endless track 34, this force istransmitted to the frame 22 via the sprocket 28 and the side plates 22Bof the frame 22 are moved in the direction of rotation. because of this,the force measuring beam 52A of the force sensor 52 is deformed in thedirection of rotation and the size of the force in the direction ofrotation is measured by the force sensor 52.

Further, when the force (lateral force) in the direction of the axis ofthe rotation is applied to the endless track 34 by the rotation of thewheel on the endless track 34, this force is transmitted to the frame 22via the planar guides 40, the balls 46, the guide plates 44, and theload bearing plate member 42, thus moving the side plates 22B of theframe 22 in the direction of the axis of the rotation. Because of this,the force measuring beam 52A of the force sensor 52 is deformed in thedirection of the axis of rotation and the size of the force in thedirection of the axis of rotation is measured by the force sensor 52.The force sensor 52 is connected to the control device 80 (see FIG. 5)and outputs the results of the measurement to the control device 80.

A pair of longitudinal sliding guide rails 62 are mounted to themounting tray beneath the bottom portion 48A of the supporting frame 48extending parallel to each other in the direction of the rotation of theendless belt (the longitudinal direction of the vehicle). A pair ofgrooves are carved in the bottom surface of the bottom portion 48 forfitting together with the longitudinal sliding guide rails 62, and thebottom portion 48A of the supporting frame 48 is fitted together withthe longitudinal sliding guide rails via the grooves. Accordingly, thesupporting frame 48 is able to move in the longitudinal direction of thevehicle along the longitudinal sliding guide frames 62.

Note that the supporting frame 48 is moved in the longitudinal directionof the vehicle closer to or further from the mounting base 12 by anunillustrated driving mechanism similar to that described earlier (aball-screw mechanism with a motor).

Note also that, of the four tire driving apparatuses 18, the directionsin which the endless tracks 34 of the pair of tire driving apparatuses18, on which sit the front wheels of the vehicle 20, rotate are parallelto each other. Moreover, the directions in which the endless tracks 34of the pair of tire rotating apparatuses, on which sit the rear wheelsof the vehicle 20, are also parallel to each other. Further, thedirection in which the endless tracks 34 of the tire driving apparatuses18, on which sit the front wheels of the vehicle, rotate is identical tothe direction in which the endless tracks 34 of the tire drivingapparatuses 18, on which sit the rear wheels of the vehicle, rotate.

As is shown in FIG. 4, pairs of wheel locking plates 64 are disposed tothe front and to the rear in the longitudinal direction of the vehicleof each tire driving apparatus 18 on the mounting tray 12 and thedriving mechanism shown in FIG. 9 is provided for each pair of wheellocking plates 64. When housed (i.e. in the state shown by the dottedlines in FIG. 9), the pairs of wheel locking plates 64 are substantiallyflush with the top surface of the mounting tray 12, and the end of eachplate in the longitudinal direction of the vehicle which is closest tothe wheel driving apparatus 18 is rotatably supported by the mountingtray 18.

A pair of levers 66 is provided for each pair of wheel locking plates64. Elongated holes 64A are formed in the middle portion in thelongitudinal direction of the vehicle of each of the side surfaces ofthe wheel locking plates 64. The upper end portion of each lever 66 ismovably held by a pin 68 in each elongated hole 64A. When the wheellocking plate 64 is housed, the bottom end portion of each of the pairsof levers 66 is rotatably supported by the mounting tray 12 in such amanner that the distance between the bottom end portion of each of apair of levers 66 is shortened, the closer to the bottom end portion ofthe lever.

Moreover, the central portions of each lever of a pair of levers 66 areconnected to each other via a hydraulic cylinder. The central portion ofone lever of each pair of levers 66 is connected to one end of anextension coil spring, the other end of which is attached to themounting tray 12.

The hydraulic cylinder 70 is connected to the control device 80 (seeFIG. 5), and is expanded and contracted by the control device 80. As thelength of the hydraulic cylinder 70 is gradually shortened to less thanthe length shown in FIG. 9, the pairs of levers 66 gradually approach anupright position against the urging force of the extension coil spring72 and the distance between the top end portions of each lever of thepairs levers 66 is gradually shortened. In accompaniment to this action,each plate of the pairs of wheel locking plates 64 begins to rotate. Asis shown by the double dot dash line in FIG. 9, when a wheel ispositioned on the tire driving apparatus 18, then as the distal endportion of each plate of the pair of wheel locking plates 64 makescontact with the wheel, rotation of the wheel in the longitudinaldirection of the vehicle is prevented.

Rods 74 are attached to the sides of the mounting tray 12 at fourpositions corresponding to the four tire driving apparatuses 18. As isshown in FIG. 10, each rod 74 is supported so as to be rotatable in thedirection indicated by the arrow A in FIG. 10, and is also able toexpand and contract. A distance sensor 76 is attached to the distal endof each rod 74. A non-contacting type of sensor, for example, one thatirradiates a laser light onto an object and detects the distance betweenitself and the object by receiving the laser light reflected back by theobject, may be used for the distance sensor 76.

When a wheel is positioned on top of the tire driving apparatus 18, eachrod 74 is either expanded or contracted and rotated manually so that thedistance sensor faces the center of the wheel. This enables the distancesensor 76 to detect the distance between itself and the wheel positionedon the tire driving apparatus 18. The distance sensor 76 is connected tothe control device 80 (see FIG. 5) and the results of the detection ofthe distance to the wheel are output to the control device 80.

A microcomputer, for example, may be used for the control device 80shown in FIG. 5. A display unit 82 comprising a CRT or the like fordisplaying the values of the measurements made by the force sensor 52,the direction in which the wheel angle is to be adjusted, and the likeis connected to the control device 80.

An explanation will now be given of the wheel alignment adjustmentmethod using the above described wheel alignment measuring apparatus asan effect of the present embodiment.

First, the operator moves the supporting frame 48 of each tire drivingapparatus 18 in the longitudinal direction of the vehicle along thelongitudinal sliding guide rails 62 so that the four tire drivingapparatuses 18 are positioned to correspond with the four wheels of thevehicle to be adjusted in accordance with the wheel base andlongitudinal tread base of the vehicle to be adjusted. The operator alsomoves the frame 22 in the transverse direction of the vehicle along thetransverse sliding guide rails and thus adjusts the position of eachtire driving apparatus 18 on the mounting tray 12.

Note here that because the above movements are performed using thedriving force of a motor via the ball-screw mechanism, if the motordrive is stopped, the tire driving apparatus 18 is locked in theadjusted position by the ball-screw mechanism.

Next, each of the wheels of the vehicle 20 is positioned on a tiredriving surface 36 of the tire driving apparatus 18 and the vehicle 20is moved on the mounting tray 12 with the steering wheel of the vehicle20 turned to the direction of rectilinear forward movement so that thecenter line of the body is substantially parallel to the direction inwhich the endless track 34 of the tire driving apparatus 18 rotates.Next, each rod 74 is manually expanded or contracted and rotated so thatthe distance sensor 76 faces the center of each of the wheels.

When the above operation is completed, the operator instructs thecontrol device 80 to measure the wheel angle. Consequently, the steps inthe wheel alignment measuring process shown in FIG. 11 are performed insequence. The vehicle orientation adjustment process shown in FIG. 12 isalso performed in cycles of a predetermined time. An explanation isgiven below of the vehicle orientation adjustment process, withreference made to FIG. 12.

In step 100, the distance between each wheel sensor 76 and the center ofeach corresponding wheel on the vehicle is measured by the distancesensors 76 (these distances are shown as a, b, A, and B in FIG. 13). Instep 102, the value obtained by subtracting the distance b from thedistance sensor 76 to the center of the left rear wheel of the vehiclefrom the distance a from the distance sensor 76 to the center of theleft front wheel of the vehicle (a-b), and the value obtained bysubtracting the distance B from the distance sensor 76 to the center ofthe right rear wheel of the vehicle from the distance A from thedistance sensor 76 to the center of the right front wheel of the vehicle(A-B) are compared, and on the basis of the comparison a determinationis made as to whether or not the orientation of the vehicle is correct.

In step 102, if the value of (a-b) is the same as the value of (A-B),then, even if the tread base of the front wheels of the vehicle 20 andthe tread base of the rear wheels of the vehicle 20 are at variance, itcan be determined that the center line of the body is parallel to thedirection in which each tire driving apparatus 18 of the wheel alignmentmeasuring apparatus rotates and the determination of step 102 isaffirmative. The vehicle orientation process is then completed with nofurther process performed.

On the other hand, if the value of (a-b) is not the same as the value of(A-B) in step 102, a negative determination is made and the routineproceeds to step 104. In step 104, the distance to be moved by the tiredriving apparatus in order for the value of (a-b) to match the value of(A-B) is calculated and, on the basis of the calculation, the motor 60is driven and the position of the tire driving apparatus 18 is adjustedby being moved in the direction of the axis of rotation. This allows theorientation of the vehicle to be adjusted so that the center line of thebody is parallel to the direction in which the tire driving apparatus 18of the wheel alignment measuring apparatus rotates. Using theabove-described process, even if the center line of the body of avehicle moved to the top of the mounting tray 12 is not parallel to thedirection in which the tire driving apparatuses 18 rotate, theorientation of the vehicle can still be corrected so that the two are inparallel.

In the wheel alignment measurement process (FIG. 11) described below,one wheel at a time of the vehicle 20 is rotated by the tire drivingapparatus 18. If one wheel at a time of the vehicle 20 is rotated, then,because of the force in the direction of the axis of rotation generatedby the rotating wheel, a distortion still arises in the non-rotatingtires minutely displacing the vehicle body and changing the alignment ofthe wheel rotating on the tire driving surface 36. However, because theafore-mentioned vehicle body orientation adjusting process is performedcyclically even when the wheel is being rotated and the vehicle bodyposture is displaced by the distortion of the tires which are notrotating and the tire driving apparatus 18 is moved in such a way thatthe alignment of the rotating wheels on the tire driving surface 36 iskept in the same state as when the vehicle body posture is notdisplaced, the alignment of the rotating wheel on the tire drivingsurface 36 is kept constant and the accuracy of the measurement in thewheel alignment measuring process is improved.

Next, the wheel alignment measuring process is explained with referencemade to the flow chart shown in FIG. 11. In step 120, the wheel lockingplates 64 of the three wheels other than the one to be measured arerotated by the hydraulic cylinder 70 to lock the three non-measuredwheels immovably in the longitudinal direction of the vehicle. Notethat, instead of locking the wheel with the wheel locking plate 64, itis also possible to use the jacking points provided in the vehicle 20 orthe like to fix the vehicle so as to prevent movement of the vehicle inthe longitudinal direction thereof. However, in this case, it isnecessary to ensure that, by this fixing of the vehicle body, any forceother than the wheel driving force does not apply to the vehicle body.

In the next step 122, the tire driving apparatus 18 of the wheel to bemeasured is rotated. This causes the wheel to be measured to rotate onthe tire driving surface 36. Accordingly, the wheel to be measuredrepeatedly travels from the top surface of the plate sections 32 up ontothe top surface of the protruding portions, and then from the topsurface of the protruding portions descends back onto the top surface ofthe plate sections 32.

The travel of the wheel up onto the top surface of the protrusion andthen back down onto the tops surface of the plate sections generateslongitudinal force Fx (force in the direction of rotation), lateralforce Fy (force in the direction of the axis of the rotation, and loadFz (vertical force onto the tire driving surface in the tire of thewheel being measured). In the present embodiment, however, of the abovethree forces, the longitudinal force Fx and the lateral force Fy aremeasured by the force sensor 52. Therefore, in step 124, the output (thevalues of the measurements of the longitudinal force Fx and the lateralforce Fy) from the force sensor 52 is sampled and the values of themeasurements of the longitudinal force Fx and the lateral force Fyobtained from the sampling is stored in a storage means such as thememory.

In the next step 126, a determination is made as to whether or not themeasuring of the wheel being measured is completed. If the determinationis negative, the routine returns to step 122 and the processes of steps122 to 126 are repeated in comparatively short cycles. The longitudinalforce Fx and the lateral force Fy generated by the wheel being measuredrotating on the tire driving surface 36 are thus measured incomparatively short cycles and the results of the measuring stored insequence until the determination of step 126 is affirmative.

When certain conditions are fulfilled, such as the passage of apredetermined time, or the completion of a predetermined number ofrotations of the tire, or the amount of data for the measurements storedin the memory has reached a predetermined amount (these conditions areset so that the continuous measuring of the longitudinal force Fx andthe lateral force Fy during the period from when the wheel rides up ontoa protruding portion until the wheel descends from the protrudingportion is performed at least once), the determination of step 126 isaffirmative and the routine proceeds to step 128. In step 128, adetermination is made as to whether or not the above measuring processhas been performed for all the wheels of the vehicle 20. If thedetermination is negative, the routine returns to step 120 and theprocesses are repeated with another wheel as the wheel to be measured.

When the measuring process has been performed for all the wheels of thevehicle and all the data for each wheel has been collected, anaffirmative determination is made in step 128. In step 130, the lock ofthe wheel locking plate 64 is released and the routine then proceeds tostep 132. In step 132, the direction of the toe angle adjustment (i.e.does the wheel need to be adjusted in the toe-in direction or thetoe-out direction) is calculated for each of the wheels of the vehicle.The calculation for one wheel is performed as described below.

Firstly, the values of the plurality of measurements of the longitudinalforce Fx and the lateral force Fy of the wheel to be processed arefetched from the values of all the measurements of the longitudinalforces Fx and the lateral forces Fy accumulated and stored in thestorage means. Next, each primary differential value in relation to thetime (dFx/dt: the rate of change of the longitudinal force Fx) iscalculated for the plurality of measured values of the longitudinalforce Fx. Note that, if the data for the primary differential value ofthe longitudinal force (dFx/dt) determined by the calculation is plottedalong a time axis, an example of the resulting wave form is shown by thethin solid line in FIG. 2.

Next, from the (series of data of the longitudinal force primarydifferential value (dFx/dt), the (series of data corresponding to whenthe wheel traveled over the step is extracted (namely, the (series of)data when the wheel traveled over the upward step and the (series of)data when the wheel traveled over the downward step are extracted). Asis also clear from FIG. 2, because the tire is hugely deformed when thewheel travels over the step, a characteristic pattern arises in the dataof the longitudinal force primary differential value (dFx/dt) in whichtwo large variations each of which occurs in the direction, namely, alarge variation in the positive direction and a large variation in thenegative direction each having a predetermined amplitude or greateroccur in sequence. Moreover, when the wheel travels over the upwardstep, a negative variation is followed by a positive variation. When thewheel travels over the downwards step, a positive variation is followedby a negative variation.

Accordingly, the extraction of the data corresponding to when thevehicle traveled over the upwards step and the downwards step can beachieved in the following way. For example, the data for an absolutevalue over a predetermined value is extracted from the data for thelongitudinal force primary differential value (dFx/dt) and thisextracted data is regarded as data for the peak or the vicinity of thepeak caused by the passage of the wheel over the step. If thecharacteristic variation pattern for the upward step or thecharacteristic variation pattern for the downward step occurs in the(series of) data obtained from the measurement within a predeterminedperiod which includes the data, then that (series of) data is extractedas the data for when the wheel traveled over the upward step or for whenthe wheel traveled over the downward step.

Next, the timing when the (absolute value of the) primary differentialvalue of the longitudinal force, after the first of the two largevariations forming the characteristic change pattern has occurred, is atthe minimum (namely, the timing when the absolute value of thelongitudinal force is at the maximum—i.e. the timing indicated by P₁ inFIG. 2) is determined from the data extracted for when the wheeltraveled over the upward step by the above process. Specifically, thedata for the boundary when the polarity (positivity or negativity) ofthe primary differential value of the longitudinal force changes (thedata, for the point in a time sequence, where the polarity of theprevious data is different to the polarity of the subsequent data) isextracted from the above-described extracted (series of) data. Thetiming determined from this data is determined to be the timing when the(absolute value of the) primary differential value of the longitudinalforce is at the minimum. This timing corresponds to the first timingdescribed in the sixth aspect of the present invention.

Next, the timing when the (absolute value of the) primary differentialvalue of the longitudinal force, after the first of the two largevariations forming the characteristic change pattern has occurred, is atthe minimum (namely, the timing when the absolute value of thelongitudinal force is at the maximum—i.e. the timing indicated by P₂ inFIG. 2) is determined from the data for when the wheel traveled over thedownward step, in the same way as the first timing. This timingcorresponds to the second timing described in the sixth aspect of thepresent invention.

Next, the values of the measurements of the lateral force Fy measuredwithin the period between the first timing and the second timing(corresponding to the predetermined period of the present invention) areextracted from the values of the measurements of the lateral force Fyfetched from the storage means and the primary differential value ofeach is calculated in relation to the time (dFy/dt: the rate of changeof the lateral force Fy). Note here that, if the data for the primarydifferential value of the lateral force (dFy/dt) determined by thecalculation are plotted along a time axis, an example of the resultingwave form is shown by the thick solid line in FIG. 2.

Next, the energy of the variation in the lateral force Fy within thepredetermined period is calculated. In the present embodiment, the sumof the square root of the primary differential value of the lateralforce (dFy/dt) is calculated to find the energy of the variation in thelateral force Fy (see the following formula).

E=Σ(dFy/dt)²

The direction of the toe angle adjustment required to reduce the energyof the variation in the lateral force (i.e. does the wheel need to beadjusted in the toe-in direction or the toe-out direction) is thencalculated on the basis of the calculated energy of the of the variationin the lateral force Fy (the sum E of the square root of the primarydifferential value of the lateral force).

Note that the optimum toe angle is the angle at which the sum E of thesquare root (the energy of the variation in the lateral force) is at theminimum, however, in order to obtain the toe angle at which the sum E ofthe square root is at the minimum, it is necessary to repeatedly measurethe longitudinal force Fx (or the load Fz) and the lateral force Fywhile altering the toe angle. Moreover, in some cases, it may bedifficult to determine the direction in which the toe angle should beadjusted from the value of the sum E of the square root obtained fromone measurement. Therefore, it is preferable to calculate the directionof the toe angle adjustment using the summation of the primarydifferential value of the lateral force S (see the following formula)together with the sum E of the square root.

S=Σ(dFy/dt)

The toe angle at which the above summation S=0 does not always match thetoe angle at which the sum E of the square root is at the minimum,however, it is close to the toe angle at which the sum E of the squareroot is at the minimum. Therefore, by calculating the direction of toeangle adjustment in combination with the summation S of the primarydifferential value of the lateral force (for example, by determining thedirection of toe angle adjustment from the summation S when thedirection of toe angle adjustment cannot be determined from the sum E ofthe square root), the number of measurements of the longitudinal forceFx (or the load Fz) and the lateral force Fy may be reduced. In step132, the direction of toe angle adjustment for each wheel of the vehicleis determined by performing each of the above-described processes.

In the next step 134, the calculated energy of the variation in thelateral force Fy (the sum E of the square root of the primarydifferential value of the lateral force), and the direction of the toeangle adjustment are displayed on the display unit 82 for each wheel,and the processes are completed temporarily. This enables the operatorto determine, on the basis of the information displayed on the displayunit 82, whether or not there is a need to adjust the toe angle of eachwheel. If there is a need to adjust the toe angle, which direction thetoe angle should be adjusted towards, and by how much.

After the operator has adjusted the toe angle of each wheel of thevehicle 20, if the toe angle needs to be checked again, an instructionis given to repeat the above-described wheel alignment measuringprocess. Subsequently, in the manner described above, a determination isagain made as to whether or not the wheel alignment after the toe angleadjustment is suitable on the basis of the longitudinal force and thelateral force. Through this method, the alignment of the wheel of thevehicle 20 can be appropriately adjusted so that, regardless of the typeof tire fitted to the vehicle 20, a high degree of running stability onan actual road surface in accordance with the characteristics of thetire can be achieved and one-sided wear resistance can be improved.

Moreover, because a combination of the tire driving apparatus 18, themain lifting apparatus 10 for lifting the vehicle 20 levelly, and asub-lifting apparatus 14 for lifting only the body of the vehicle 20 wasemployed for the wheel alignment measuring apparatus, the apparatus canalso easily be used for changing tires or for vehicle maintenance.

Note that in the above description, the longitudinal force Fx and thelateral force Fy are measured and the predetermined time is determinedon the basis of the transition of the rate of change of the longitudinalforce Fx (the primary differential value of the longitudinal forcedFx/dt), and the energy of the variation in the lateral force Fy withinthe predetermined time was then calculated, however, the presentinvention is not limited to this. As is made clear by comparing FIGS. 2and 3, the rate of change in the load Fz (the primary differential valueof the load dFz/dt) whenever the wheel travels in sequence over theupward step and the downward step changes in the same way as the rate ofchange in the longitudinal force Fx (except that the positivity andnegativity of the variation are reversed). Therefore, it is possible toprovide a force sensor with a structure capable of measuring both theforce in the direction of the axis of rotation of the endless track 34(the lateral force Fy) and the force in the direction orthogonal to boththe direction of the axis of rotation and the direction of rotation (theload Fz), to measure the load Fz instead of the longitudinal force Fx,to determine the predetermined period on the basis of the transition ofthe rate of change in the load Fz, and to calculate the energy of thevariation in the lateral force Fy within this predetermined period.

Further, the explanation given above is for when a force sensor fordetecting force in two directions (longitudinal force Fx or load Fz, andlateral force Fy) is used, however, the present invention is not solimited. When the period for calculating the energy of the variation inthe lateral force Fy (the predetermined period) is to be determined onthe basis of, for example, the longitudinal force Fx and the load Fz, itis possible to provide a force sensor with a structure capable ofmeasuring force in three directions (longitudinal force Fx, lateralforce Fy, and load Fz) and using this force sensor to measure thelongitudinal force Fx, lateral force Fy, and load Fz.

Moreover, the explanation given above is for when, on the basis of thetransition of the rate of change in the longitudinal force (or load),the first timing, which is when the rate of the change (the primarydifferential value) of the longitudinal force or load caused by the tiredeforming as the wheel climbs up onto a protrusion returns to theminimum after changing to a predetermined value or more (the timingindicated by P₁ in FIGS. 2 and 3), and the second timing, which is whenthe rate of the change in the longitudinal force or the load caused bythe tire on a wheel deforming as the wheel descends from the protrusionreturns to the minimum after changing to a predetermined value or more(the timing indicated by P₂ in FIGS. 2 and 3) are determined and theenergy of the variation in the lateral force is calculated within thepredetermined period from the first timing until the second timing,however, it is sufficient if the period for calculating the energy ofthe variation in the lateral force (the predetermined period of thepresent invention) includes the time from when the tire is deformed bythe wheel travelling over the step until the tire rotates and returnssubstantially to its normal state. Accordingly, the period forcalculating the energy of the variation in the lateral force is notlimited to the period described above, and the second timing of thepredetermined period may be determined as being the time when, forexample, the front edge portion of the road-contacting surface of thetire is no longer in contact with the protruding surface (i.e. thetiming corresponding to the peak of the portion of the primarydifferential value of the longitudinal force or lateral force beingabove a predetermined value immediately before the point P₂ in FIGS. 2and 3), and the energy of the change in the lateral force calculated forthis period.

In addition, according to the present invention, it is sufficient if atleast the energy of the variation in the lateral force during the periodfrom when the tire is deformed by the wheel travelling over the step(preferably, the upward step) until the tire rotates and returnssubstantially to its normal state. Because of this, instead of measuringthe longitudinal force Fx or the load Fz, it is possible to detect thetiming when the wheel travels over the step by detecting thedisplacement of the tire in, for example, the vertical direction and, onthe basis of the time lapsed from that timing, to determine the timingwhen the tire rotates and returns substantially to its normal state.

The explanation given above was also for an example in which an upwardstep and a downward step are formed on a tire driving surface byproviding a protrusion 38 on plate sections 32 forming theabove-described tire driving surface, however, the present invention isnot limited to this, and the step may be formed on the tire drivingsurface by, for example, altering the thickness of a portion of theplate sections 32, as is shown in FIG. 14. In the tire driving apparatusshown in FIG. 14, when looking from the direction in which the wheelrotates on the tire driving surface (the opposite direction to thedirection in which the endless track 34 rotates, i.e. the oppositedirection to that indicated by the arrow B in FIG. 14), four platesections 32A˜32D are formed and arranged continuously in the directionof rotation in such a way that the height of the tire driving surface issuddenly raised up and then gradually returns to the original height. Astep (corresponding to the step described in the third aspect of thepresent invention) is formed between the normal plate sections 32 whichare positioned downstream from the plate section 32A in the direction inwhich the endless track rotates and the plate section 32A (the topsurfaces of the plate sections 32A˜32D correspond to the protrudingsurface described in the third aspect of the present invention). In thiscase, the wheel rotating on the tire driving surface travels over theupward step only, however, because the change in the energy of thevariation in the lateral force due to the wheel angle is larger when thewheel travels over the upwards step, so that even if a tire drivingapparatus having the structure shown in FIG. 14 is used, the alignmentof the wheel can be accurately adjusted to the appropriate wheel angle.

In the example given in the above explanation, a motor was mounted tothe outside of the tire driving apparatus, however, a built-in typeroller may also be used having the motor fitted inside the drivingroller.

The example given in the above explanation also described an endlesstrack 34 having a driving surface which was formed from connected platesections 32, however, the present invention is not limited to this, andseveral other structures may be used. For example, as is shown in FIG.15A, the outer surface of a large-scale roller 86 may be used as thetire driving surface and planar-like protrusion 88 is mounted on theouter surface of the roller 86 so as to form a step, or, as is shown inFIG. 15B, the outer surface of an endless belt 90 may be used as thetire driving surface, and planar protrusions 92 attached to the outersurface of the endless belt 90. Alternatively, as illustrated in FIG.15C, an endless belt 94 may be formed having a thickness which steadilyincreases or decreases at a substantially constant rate of change in thecircumferential direction and having a portion at a predeterminedposition in the circumferential direction on the outer surface where thethickness abruptly changes. Thus, in the same way as in the tire drivingapparatus in FIG. 14, the tire driving surface and the step 96 (i.e. theportion where the thickness abruptly changes) are formed integratelytogether. Note that the present invention is not limited to the numberor shape of protrusion or step described in the above examples, andthese may be suitably varied provided that the operations and effects ofthe present invention are not hindered.

In the above explanation, a vehicle and a tire driving surface wererotated relative to each other by rotating the tire driving surface (thewheel rotating surface) and the wheel being rotated on the tire drivingsurface, however, the present invention is not limited to this, and thefollowing method may be used. At least one protrusion is mounted on aroad surface. Sensors for detecting the longitudinal force, or the load,and the lateral force generated in a tire are attached to the vehicleand the car is driven so that the wheels travel over the protrusionmounted in the road. The wheel angle is then adjusted on the basis ofthe results of the measurements of the longitudinal force, or the load,and the lateral force by the sensors attached to the vehicle. Moreover,instead of mounting protrusions on the road surface, it is possible toform a wheel rotating surface by providing rectangular, plain-bottomedgrooves in the road surface. In this case, if the size of the opening ofthe grooves is of a sufficient length for the wheel to be able to rotateon the bottom of the groove, then the edge of the groove acts as a stepallowing adjustment of the wheel angle to be performed in the same wayas when the protrusion are mounted on the road surface. The first andsecond aspects of the present invention include the above embodimentswithin the scope of their aspects.

In the above explanation, the tire was deformed by rotating the wheel ona wheel rotating surface having a step formed thereon, and thenmeasuring the lateral force generated in the tire. However, the presentinvention is not so limited. In a vehicle having equal or more than fourwheels, by changing the position of one wheel in substantially avertical direction relative to the other wheels, the load acting on eachwheel of the vehicle changes and a deformation is caused in the tire.Therefore, for example, by the wheel to be measured being displacementin substantially the vertical direction so as to change the load actingon the wheel being measured, the tire on the wheel being measured isdeformed without using a step and the lateral force and load generatedin the tire may be measured.

Making displacement the tire in substantially the vertical direction canbe achieved, as is shown in FIG. 16, by providing a structure in whichcams 78 are provided beneath the tire driving apparatus 18 so as to bein contact with the tire driving apparatus 18. The tire drivingapparatus 18 is supported by the cams 78, and then the cams 78 arerotated so that the tire driving apparatus 18 is moved up and down. Inthe above structure, when the cams 78 are rotated to the position shownby the dotted lines in FIG. 16, the wheels are displaced upwards insubstantially the vertical direction via the tire driving apparatus 18,thus deforming the tire. However, in order to accurately measure thevariation in the lateral force (and load) generated in the tire, it isnecessary to rotate the cams within a comparatively short time to causethe load acting on the wheel to change a predetermined amount or morewithin a predetermined time. Moreover, in this case, because there ishardly any change in the longitudinal force, it is also possible tomeasure the load generated in the tire for a certain period includingthe timing when the cam is rotated and a period before and after thattiming, and the results of the measurement of the load are compared tothe load generated in the tire when the tire is in substantially anormal state (the load reference value). The period when a differencebetween the reference value and the measured value exists is determinedas being the period for calculating the energy of the variation in thelateral force (the predetermined period). This aspect corresponds to theseventh and eighth aspects of the present invention.

Moreover, the sum E of the square root of the rate of change in thelateral force Fy within a predetermined period (the primary differentialvalue dFy/dt) is obtained as the energy of the variation in the lateralforce within a predetermined period, however, the present invention isnot limited to this. For example, as the energy of the variation in thelateral force: the summation of the absolute value of the primarydifferential value of the lateral force Fy within the predeterminedperiod (=Σ|dFy/dt|); the summation of the secondary differential valueof the lateral force Fy within the predetermined period (=Σd²Fy/dt²);the summation of the square root of the secondary differential value ofthe lateral force Fy within the predetermined period (=Σ(d²Fy/dt²)²);the summation of the absolute value of the secondary differential valueof the lateral force Fy within the predetermined period (=Σ|d²Fy/dt²|);the summation of the tertiary differential value of the lateral force Fywithin the predetermined period (=Σd³Fy/dt³); the summation of thesquare root of the tertiary differential value of the lateral force Fywithin the predetermined period (=Σ(d³Fy/dt³)²) and the like may beobtained, and an arbitrary physical amount corresponding to the energyof the variation in the lateral force can be used.

In the explanation given above, the toe angle was adjusted for eachwheel by an operator on the basis of the direction of toe angleadjustment displayed on the display unit 82. However, the presentinvention is not so limited. Generally, the steering wheel of a vehicleis structured so that the toe angle can be adjusted, however, there arealso vehicles which are not structured so that the toe angle can beadjusted for each wheel other than the steering wheel, and there arealso vehicles which are structured so not only that the toe angle cannotbe adjusted for each wheel other than the steering wheel, but also thatthe toe angle cannot be adjusted for the wheels per each of axle. Incases such as this, it is possible to adjust the angle between the axleand the vehicle body on the basis of the information displayed on thedisplay unit 82 so that the energy of the variation in the lateral forcegenerated in a tire within a predetermined period according to thepresent invention is made substantially equal for each of pair of wheelsmounted on the axle.

The main lifting apparatus 10 and the sub-lifting apparatus 14 of thewheel alignment measuring apparatus may also have an integratedstructure. Moreover, the wheel alignment measuring apparatus may bestructured having a tire driving apparatus 18 mounted on a turningapparatus which is capable of turning around a vertical axis and whichis capable of displaying the turning angle or outputting the turningangle as a signal. In this case, by repeating in sequence a process ofrotating the wheel using the tire driving apparatus 18 and collectingthe data, and a process of turning the turning apparatus (this actionequates to changing the toe angle of the wheel), it becomes possible, onthe basis of the collected data, to achieve an optimum toe angle valueregardless of the direction in which the toe angle is to be adjusted.

If the vehicle to be adjusted is capable of having the camber anglethereof which is able to be adjusted, it is possible to adjust thecamber angle within the range permitted by the design specifications.When the camber angle is adjusted, it is preferable if a conventionallyknown alignment measuring apparatus or an angle measuring device such asan angle meter is used in combination with the above-described wheelalignment measuring apparatus, as the work efficiency is therebyimproved.

The explanation above was for an example in which two pairs of tiredriving surfaces were used, however, it is possible to use one pair oftire driving surfaces and adjust only the alignment of the steeringwheel or adjust the alignment for each of the front and rear axles.

What is claimed is:
 1. A method of adjusting a wheel alignment of avehicle, comprising the steps of: rotating a vehicle and a wheelrotating surface relatively in such a manner that a wheel of a vehicleto be adjusted with a tire fitter thereto is rotated in a proceedingdirection of the vehicle over the wheel rotating surface which has astep of a predetermined height formed thereon so that the wheel passesover the step, measuring a lateral force generated in the tire of thewheel, and adjusting a wheel angle so that an energy of a variation inthe lateral force which is related to a rate of change of said lateralforce and is generated in the tire during a predetermined periodincluding a time from when the tire is deformed at the wheel passingover the step until the tire rotates and returns substantially to normalstate is within a predetermined range which includes a minimum value ofthe energy of the variation in the lateral force.
 2. A method ofadjusting a wheel alignment of a vehicle according to claim 1, whereinthe wheel rotating surface comprises: a base surface; and a protrudingsurface which is positioned on a downstream side of the base surface ina direction in which the wheel rotates, and whose height at least at aposition where the step is formed by the base surface and the protrudingsurface is greater than the base surface by a predetermined amount.
 3. Amethod of adjusting a wheel alignment of a vehicle according to claim 2,wherein the protruding surface is a top surface of a substantially plateshaped protrusion whose height is a predetermined height above the basesurface, and the protrusion is formed so that the protruding surfaceextends long enough in a direction of a relative movement of the vehicleand the wheel rotating surface for both ends of a ground-contactingportion of the tire in the direction of the relative movement to be incontact with the protruding surface when the wheel passes over theprotrusion.
 4. A method of adjusting a wheel alignment of a vehicleaccording to claim 1, wherein the wheel rotating surface is an outerperipheral surface of an endless track which is driven to rotate, andthe step is provided at least at one location on the wheel rotatingsurface along a direction in which the endless track rotates, and thewheel of the vehicle to be adjusted is placed on the wheel rotatingsurface and the endless track is driven to rotate so that the wheel ofthe vehicle to be adjusted is rotated, thereby moving the vehicle andthe wheel rotating surface relatively.
 5. A method of adjusting a wheelalignment of a vehicle according to claim 1, wherein a plurality ofmeasurements are made of the lateral force in a period for measuring thelateral force, and determining the energy of the variation in thelateral force generated in the tire of the wheel within thepredetermined period by calculating and adding of, on the basis of thelateral force measured at each measurement within the predeterminedperiod, at least one of a square root of a primary differential value ofthe lateral force at each measurement, or an absolute value of theprimary differential value of the lateral force at each measurement, ora secondary differential value of the lateral force, or a square root ofthe secondary differential value of the lateral force, or an absolutevalue of the secondary differential value of the lateral force, or atertiary differential value of the lateral force, or a square root ofthe tertiary differential value of the lateral force.
 6. A method ofadjusting a wheel alignment of a vehicle according to claim 1, whereinthe energy of the variation in the lateral force relates to adifferential value of the lateral force.
 7. A method of adjusting awheel alignment of a vehicle, comprising the steps of; rotating avehicle and a wheel rotating surface relatively in such a manner that awheel of a vehicle to be adjusted with a tire fitted thereto is rotatedin a proceeding direction of the vehicle over the wheel rotating surfacewhich has a step of a predetermined height formed thereon so that thewheel passes over the step, measuring at least one of a longitudinalforce or a load generated in the tire and a lateral force generated inthe tire of the wheel, determining a predetermined period including atime from when the tire is deformed at the wheel passing over the stepuntil the tire rotates and returns substantially to normal state basedon the measurement of at least one of the longitudinal force or theload, and adjusting a wheel angle so that an energy of a variation inthe lateral force which is related to a rate of change of said lateralforce and is generated in the tire during the predetermined period iswithin a predetermined range which includes a minimum value of theenergy of the variation in the lateral force.
 8. A method of adjusting awheel alignment of a vehicle according to claim 7, wherein the wheelrotating surface comprises: a base surface; and a protruding surfacewhich is positioned on a downstream side of the base surface in adirection in which the wheel rotates, and whose height at least at aposition where the step is formed by the base surface and the protrudingsurface is greater than the base surface by a predetermined amount.
 9. Amethod of adjusting a wheel alignment of a vehicle according to claim 8,wherein the protruding surface is a top surface of a substantially plateprotrusion whose height is a predetermined height above the basesurface, and the protrusion is formed so that the protruding surfaceextends long enough in a direction of a relative movement of the vehicleand the wheel rotating surface for both ends of a ground-contactingportion of the tire in the direction of the relative movement to be incontact with the protruding surface when the wheel passes over theprotrusion.
 10. A method of adjusting a wheel alignment of a vehicleaccording to claim 8, wherein the protruding surface is a top surface ofa substantially plate shaped protrusion whose height is a predeterminedheight above the base surface, and the protrusion is formed so that theprotruding surface extends long enough in a direction of a relativemovement of the vehicle and the wheel rotating surface for both ends ofa ground-contacting portion of the tire in the direction of the relativemovement to be in contact with the protruding surface when the wheelpasses over the protrusion, and the predetermined period is determinedto be a period from a first timing until a second timing, the firsttiming is when a rate of a change at least one of in the longitudinalforce or the load as the wheel climbs up onto the protrusion with thetire of the wheel deforming becomes a minimum after changing to apredetermined value or more, the second timing is one of when the rateof the change at least one of in the longitudinal force or the loadbecomes to a minimum after changing to a predetermined value or more, orwhen a front end of the ground-contacting portion of the tire in thedirection of the relative movement is without contacting with theprotruding surface as the tire rotates on the protruding surface and thewheel descends from the protrusion with the tire of the wheel deforming.11. A method of adjusting a wheel alignment of a vehicle according toclaim 7, wherein the wheel rotating surface is an outer peripheralsurface of an endless track which is driven to rotate, and the step isprovided at least at one location on the wheel rotating surface along adirection in which the endless track rotates, and the wheel of thevehicle to be adjusted is placed on the wheel rotating surface and theendless track is driven to rotate so that the wheel of the vehicle to beadjusted is rotated, thereby moving the vehicle and the wheel rotatingsurface relatively.
 12. A method of adjusting a wheel alignment of avehicle according to claim 7, wherein a plurality of measurements aremade of the lateral force in a period for measuring the lateral force,and determining the energy of the variation in the lateral forcegenerated in the tire of the wheel within the predetermined period bycalculating and adding of, on the basis of the lateral force measured ateach measurement within the predetermined period, at least one of asquare root of a primary differential value of the lateral force at eachmeasurement, or an absolute value of the primary differential value ofthe lateral force at each measurement, or a secondary differential valueof the lateral force, or a square root of the secondary differentialvalue of the lateral force, or an absolute value of the secondarydifferential value of the lateral force, or a tertiary differentialvalue of the lateral force, or a square root of the tertiarydifferential value of the lateral force.
 13. A method of adjusting awheel alignment of a vehicle according to claim 7, wherein the energy ofthe variation in the lateral force relates to a differential value ofthe lateral force.
 14. A method of adjusting a wheel alignment of avehicle, comprising the steps of; rotating a wheel of a vehicle to beadjusted with a tire fitted thereto on a wheel rotating surface in aproceeding direction of the vehicle, changing a load acting on thevehicle by a predetermined amount or more within a predetermined period,and measuring a lateral force generated in the tire on the wheel, andadjusting a wheel angle in such a way that an energy of a variation inthe lateral force generated in the tire during a predetermined periodwhich includes a time from when the tire of the wheel is deformed with achange in the load until the tire rotates and returns substantially tonormal state is within a predetermined range which includes a minimumvalue of the energy of the variation.
 15. A method of adjusting a wheelalignment of a vehicle according to claim 14, wherein the wheel rotatingsurface is a substantially planar surface, and the vehicle and the wheelrotating surface are rotated relatively in such a way that the wheelrotates on the wheel rotating surface, the load acting on the wheel ischanged by displacing the wheel in substantially a vertical directionvia the wheel rotating surface, measuring the load and the lateral forcegenerated in the tire of the wheel, and the predetermined period isdetermined by comparing the result of the measurement of the load with aload generated in the tire when the tire of the wheel is substantiallynormal state.
 16. A method of adjusting a wheel alignment of a vehicleaccording to claim 14, wherein a plurality of measurements are made ofthe lateral force in a period for measuring the lateral force, anddetermining the energy of the variation in the lateral force generatedin the tire of the wheel within the predetermined period by calculatingand adding of, on the basis of the lateral force measured at eachmeasurement within the predetermined period, at least one of a squareroot of a primary differential value of the lateral force at eachmeasurement, or an absolute value of the primary differential value ofthe lateral force at each measurement, or a secondary differential valueof the lateral force, or a square root of the secondary differentialvalue of the lateral force, or an absolute value of the secondarydifferential value of the lateral force, or a tertiary differentialvalue of the lateral force, or a square root of the tertiarydifferential value of the lateral force.
 17. A method of adjusting awheel alignment of a vehicle, comprising the steps of; rotating avehicle and a wheel rotating surface relatively in such a manner that awheel of a vehicle to be adjusted with a tire fitted thereto is rotatedin a proceeding direction of the vehicle over the wheel rotating surfacewith a tire of a wheel deforming, measuring a lateral force generated inthe tire of the wheel, and adjusting a wheel angle so that an energy ofa variation in the lateral force which is related to a rate of change ofsaid lateral force and is generated in the tire during a predeterminedperiod including a time from when the tire is deformed until the tirerotates and returns substantially to normal state is within apredetermined range which includes a minimum value of the energy of thevariation in the lateral force.
 18. A method of adjusting a wheelalignment of a vehicle according to claim 17, wherein the energy of thevariation in the lateral force relates to a differential value of thelateral force.